Sample pipette

ABSTRACT

Sample pipettes used in particular for injecting samples into high pressure liquid chromatography apparatuses, which are provided with a hollow needle for drawing a sample and expelling same into a container or into a sample receiving device of the apparatus. An interchangeable cannula is mounted on the hollow needle of such a pipette, said cannula being capable of containing additional functional elements such as filters, chemically active phases and the like.

FIELD OF THE INVENTION

The invention concerns a sample pipette having a hollow needle fordrawing a liquid volume, such as a sample, a reagent, etc., and forexpelling the same into a container or into a sample receiving device ofan analysis apparatus, in particular for injecting the sample into aHPLC apparatus.

BACKGROUND OF THE INVENTION

Frequently, a sample preparation is required between a sample extractionand the input of the sample into a chromatography apparatus. For theassociated necessary processing steps, such as filtering, separating oradding individual components, the sample has to be expelled from theextraction pipette into a processing container and, after theprocessing, drawn into a sample injector pipette.

A plurality of processing steps are costly and increase the risk offailures, contaminations, etc. Therefore, there exists basically a needfor simplification also in the range of the sample preparation. Theinvention is based on this requirement.

SUMMURY OF THE INVENTION

According to the invention, a simplification is achieved by aninterchangeable cannula consisting of an injection needle and anattachment part, mounted on the hollow needle, and being provided withfunctional elements, such as filters, coatings having active phases andthe like.

As a rule, in the medical and related fields the term cannula isunderstood as describing an injection needle being adapted for injectingat one end and being provided with a sticking cone for connection with asyringe and the like at the other end. In the following descriptions,the term is used similarly, wherein there exists a special attachmentpart instead of the sticking cone. For distinguishing from the hollowneedle of the syringe, the term injection needle is used for the one ofthe cannula.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

The following embodiments of the invention will be described byreferring to the appended drawings, wherein:

FIG. 1 shows a sample injector pipette having a mounted exchangeablecannula;

FIG. 2 shows a sectional illustration of the composed cannula; and

FIG. 3 shows a sectional elevational view of the single components ofthe cannula;

DETAILED DESCRIPTION OF THE DRAWING FIGURES

FIG. 1 shows the sample of the injector pipette in the shape of asyringe for manual sample injection into a HPLC apparatus. Essentially,the pipette consists of a cylinder 1, at one end 2 of which a hollowneedle 4 connected to the inner space 3 thereof is arranged, and of aplunger 5 being movable axially in the inner space, which is operatedfrom the other end 6 of the cylinder. Pipettes not being operatedmanually, but being a part of a system being operated by a machine,differ basically only negligibly therefrom. Therefore, the inventiondescribed in the following may be readily applied to a system operatedby a machine.

A cannula 7 is arranged on the free end of the hollow needle 4, which isonly sticked thereon and, therefore, can be easily exchanged. Thecannula 7 is constructed for one single use, i.e. as a rule, a newcannula is used for each new sample. For certain working steps, it maybe useful to exchange the cannula even between the drawing and theexpelling of a sample, as it will be described below.

The cannula 7 shown in the sectional views in FIGS. 2 and 3 consists ofan injection needle 8 and an attachment part 9. The attachment part 9consists of a receiving sleeve 10, a sticking sleeve 11 being coaxiallyarranged therein and a functional element 12 arranged therebetween.

On one side, the receiving sleeve 10 is connected fixedly with theinjection needle 8. From the other side thereof, a boring 13 beingweakly conical extends to the injection needle 8. Essentially, thereceiving sleeve 10 has the shape of the sticking cone of the Luer-typebeing known from commercially available cannulas. For the sake ofsimplicity, therefore, such commercially available cannulas can be used.

The sticking sleeve 11 has a conical outer wall 14 corresponding to theboring 13 and a continuous axial channel 15. At its end facing to thereceiving sleeve, the channel 15 is expanded to a cylindrical chamber 16which serves for receiving the functional element 12. A funnel-shapedextension 17 is formed at the other end of the channel 15, whereby theinsertion of the hollow needle 4 is alleviated during exchanging thecannula. The centre part 18 of the channel 15 between the chamber 16 andthe extension 17 is weakly conical or cylindrical and narrow so that itencloses tightly the hollow needle of the syringe. A narrow pass orbottleneck 19 is provided in front of the chamber for limiting theinjection depth of the hollow needle.

The closed sides of the chamber 16 and the boring 13 are deepenedconically. This results in flat cavities on both sides of the mountedfunctional element 12, which remain free.

For example, the functional element 12 comprises a filter. This servesfor filtering a sample during drawing so as to separate components ofthe sample not being desired. In order to avoid contamination during thefollowing injection of the thus filtered sample of the filteredcomponents to be taken into an analysis apparatus, the cannula used fordrawing is advisably removed or replaced by a new cannula with orwithout a filter.

An even distribution of the sample onto the complete active section isachieved by the flat cavities on both sides of the functional element12.

It is also possible to draw a sample without a filter and, thereafter,to mount a cannula with a filter for filtering the sample during thesample injection.

The functional element 12 can be also a pack having an active phase,where components of the sample are adsorbed. These components can besolved again in a following step by a suitable solvent. As forfiltering, these working steps are possible both during drawing andduring expelling.

By a combination of the various steps and elements, a plurality oftreatments of the samples may be realized. Therefore, a pipette providedwith this cannula may be used for the sample preparation in a veryadvantageous manner. Samples which are treated by one or two variouscannulas during drawing and expelling are delivered into a container,such as a cuvette of a micro titer plate, and, there, they are furtherprocessed by mixing and the like, before they are input into an analysisapparatus.

An essential advantage of the sample pipette according to the inventionconsists obviously in the fact that the liquid volume after the drawinginto the hollow needle is present on the other side of the cannula.Thereby, it is possible to replace the cannula by another cannula beforeexpelling.

Of course, the attachment part can also take shapes being different fromthe ones being shown in the present embodiment. For special steps duringprocessing samples, there may be also provided cannulas, the attachmentpart of which comprises a larger inner volume. By use of such a cannula,a liquid volume can be only drawn into the cannula. For example, thiscan be useful if there exists already a sample within the hollow needleand a mixing shall be done during expelling.

1. Sample pipette comprising a cylinder with a plunger being axiallymoveable inside the cylinder and being operated from a first end of thecylinder, a hollow needle for drawing a liquid volume into the cylinderand subsequently expelling it into a container or a sample receivinginput of an analysis apparatus, the hollow needle being arranged at thesecond end of the cylinder, and an exchangeable cannula removeablyfitted to a free end of the hollow needle, the cannula comprising aninjection needle and, an attachment part fixedly connected to one end ofthe injection needle, the attachment part comprising a channel forreceiving and tightly enclosing the tip of the hollow needle and housinga functional element.
 2. Sample pipette according to claim 1, whereinthe functional element comprises a filter.
 3. Sample pipette accordingto claim 1, wherein the functional element comprises a chemically activephase.
 4. Cannula for being attached to the tip of a hollow needle on asample pipette comprising an injection needle and an attachment partfixedly connected to one end of the iniection needle, the attachmentpart comprising a channel for receiving and tightly enclosing a tip ofthe hollow needle and housing a functional element.
 5. Cannula accordingto claim 4, wherein the functional element comprises a filter. 6.Cannula according to claim 4, wherein the functional element comprises achemically active phase.